1. Field of the Invention
The present invention relates to an illumination key for use in various mobile communication devices, such as cellular phones and automobile phones, and various terminal devices, such as electronic organizers and the like, to enable the keys thereof to be visible in nighttime and low light conditions. The present invention further relates to a method of manufacturing such illumination key.
2. Description of the Prior Art
In the prior art, this type of illumination key is constructed by forming a printed pattern layer, such as a character or the like, into the underside surface of a key top made of light-permeable resin and then fixing a silicon rubber key operating portion to the back side of the printed pattern layer by means of silicon rubber and an adhesive having good adhesive properties.
Further, in the case where a printed pattern layer, such as a character or the like, is formed in the surface of the key top, the etching of the character is carried out with a laser beam, and this makes such prior art illumination keys expensive to manufacture.
Furthermore, because prior art illumination keys are not designated to allow for reduction in size and weight of the key unit when manufacturing thin key tops, it is not possible to meet the market needs for ultralight key tops.
Moreover, because the printed pattern (character) layer is formed in the underside surface of the light-permeable resin key top, the printed pattern (character) is difficult to see in the illumination key described above in the case where the upper surface of the key top has a curved shape.
Furthermore, because the printed pattern (character) is etched by means of a laser beam, it is not possible to prevent high costs when manufacturing such illumination keys.
Moreover, in the case where a printed pattern (characters) is formed on one side of a film which is placed over a plurality of light-permeable resin key tops and heat fused to the upper and side surfaces thereof, because the key tops are connected to each other via the film, misoperations can occur when the operation of one key top also operates a neighboring key top.
Further, when designing a lightweight key top, it is difficult to adequately bond the key top and the key operating portion.
With a view towards overcoming the problems of the prior art discussed above, it is an object of the present invention to provide an illumination key which makes it possible to reliably recognize a printed pattern (character) even when the upper surface of the key top is slanted or curved, in which a key operating portion is given a rubber-like click sensitivity and a rubber-like elasticity, the key top portion is made from a rigid resin, and a reliably strong bond is created between the key operating portion and the key top.
It is a further object of the present invention to provide an illumination key and a method of manufacturing such illumination key which makes it possible to easily manufacture a printed pattern without laser etching and which makes it possible to reliably carry out ON/OFF operations for one illumination key without affecting (operating) any of the neighboring keys, in which a key operating portion is given a rubber-like click sensitivity and a rubber-like elasticity, the key top portion is made from a rigid resin, and a reliably strong bond is created between the key operating portion and the key top.
Furthermore, it is an object of the present invention to provide an illumination key that can reliably achieve ON/OFF operations while making it possible to reduce the weight of the key top without reducing the bonding strength between the key top and the key operating portion.
In order to achieve these objects, the illumination key according to the present invention is constructed from a key top made of light-permeable resin; a film having a printed pattern (character) formed in the upper or the bottom surface of the film, the film being fixed to the top and side surfaces of the key top and cut away form the lower periphery of the side surfaces of the key top; a light-permeable keypad having an operating portion and a non-operating portion, while the non-operating portion is connected to the operating portion through a thin portion; and a key operating portion made of light-permeable silicon rubber or thermoplastic elastomer which is fixed to the underside surface of the key top by means of a transparent adhesive.
In this structure, the film has thickness of 100 um-200 um, with the printed pattern being provided on either the top or bottom surface of the film.
Further, in the method of manufacturing the illumination key according to the present invention, a film having a printed pattern (character) formed in one side thereof is set inside a metal mold, and then injection molding is carried out by injecting a light-permeable resin into the cavity to form a key top, whereby the film formed with the printed pattern layer is heat fused to the upper surface of the key top. Next, after a jig is used to cut away the film from the lower periphery of the key top, a transparent adhesive is used to fix the underside surface of the key top to the upper surface of a key operating portion made from a light-permeable silicon rubber or thermoplastic elastomer.
Further, in the illumination key to the present invention, it is possible to form a partial transmission type light reflection membrane having a white color or the like on all surfaces excluding the underside surface of the light-permeable resin key top, with the printed pattern (character) layer being formed in the upper surface of such a partial transmission type reflection membrane. In this case, except for the printed pattern (character) portion, an opaque layer is provided to cover the upper and side surfaces of the key top, with the upper and side surfaces of the opaque layer being covered by a transparent protection layer. And as before, a transparent adhesive is used to fix the underside surface of the key top to the upper surface of a key operating portion made of light-permeable silicon rubber or thermoplastic elastomer.
Further, in the illumination key according to the present invention, it is possible to use a thin key top made from a white-colored or a colored partial light-permeable resin, with the printed pattern (character) being formed on a surface of the key top which excludes the underside thereof. And as before, a transparent adhesive is used to fix the underside surface of the key top to the upper surface of a key operating portion made of light-permeable silicon rubber or thermoplastic elastomer.
In the illumination key according to the present invention, an operating shaft is formed at a central portion of the underside of a transparent resin key top mounted and bonded on top of a key operating portion formed from a transparent rubber or thermoplastic elastomer, and a cavity portion is formed in the underside of the key tops in order to make the key top thinner.
Further, the transparent resin key top formed with the operating shaft is formed from a hard foaming resin such as polyurethane foam or the like.
Furthermore, the lower portion of the operating shaft of the transparent resin key top is fitted into a concave portion formed in a central upper surface portion of the transparent rubber or thermoplastic elastomer key operating portion, with such fitting portion being bonded by a transparent adhesive.
Further, in the illumination key according to the present invention, a protruding portion is formed at the central upper surface portion of the transparent rubber or thermoplastic elastomer key operating portion, and also formed in such central portion is an insertion hole into which is fitted the operating shaft of the transparent resin key top, with such fitting portion being bonded by a transparent adhesive.
Further, in the illumination key according to the present invention, an annular erect flange is formed near the outer periphery of the upper surface of the transparent rubber or thermoplastic elastomer key operating portion, and the outer circumferential surface of the annular erect flange is bonded by means of an adhesive to a contact surface of the outer peripheral surface of the inside of the cavity portion of the transparent resin key top.